In the past, Applicant has developed sheet binding systems wherein folded sheets are bound together along the fold line by means of exposed pre-applied adhesive. Applicant has received two patents covering certain aspects of this concept, to wit U.S. Pat. No. 4,525,116, issued Jun. 25, 1985 and U.S. Pat. No. 4,975,011, isssued Dec. 4, 1990. One of these systems (U.S. Pat. No. 4,525,116) discloses a system for attaching a plurality of folded sheet units along the fold lines by means of a pre-applied ribbon of heat responsive adhesive and the other system (U.S. Pat. No. 4,975,011) attaching the folded sheets along the fold line by means of a solvent activated adhesive pre-applied along the fold line thereof.
In both of these prior systems, a ribbon of adhesive is pre-applied to a double sheet unit which is then folded to bisect the ribbon of adhesive and expose the same along the marginal edge portion of the fold line. This folded sheet unit forms a pair of adjacent sheets which are then connected to other similarly folded assembled sheet units by activating the exposed pre-applied adhesive, either by means of heat or by means of a solvent.